1. Technical Field
The present invention relates to state detection devices, electronic apparatuses, measurement system and programs.
2. Related Art
Techniques for detecting the state of a user (for example, the state of exercise, etc.), with a device having various sensors attached to the body of the user, are widely used. Such devices include a heart rate monitor that detects user's heart rate information, a pedometer that estimates the number of steps while walking or running, etc.
Pedometers in recent years not only count the number of steps but also estimate other information such as the moving speed, the traveled distance, etc. of the user. It is desirable to estimate the state of the user (more concretely, as to whether the user is in the state of walking or running) in order to improve the accuracy in estimating the speed and the distance. This is because, for example, although it is necessary to use an appropriate value as the pace when the distance is calculated by the number of steps×the pace, the pace is different generally in the walking state and in the running state. This similarly applies when the speed, etc. are estimated by using parameters other than the pace. By switching the parameter in the walking state and in the parameter in the running state, an improvement in the accuracy of estimation results can be expected.
Moreover, the discrimination between the walking state and the running state is also effective in other cases besides the speed and the distance. For example, it is necessary to change the calculation method (for example, the calculation formula) depending on the load of exercise, in the case where the calorie consumption of the user is to be calculated.
In addition, because there are various processes where switching of the content is desirable between the walking state and the running state, there are strong demand for accurately judging the state of walking or running.
There have been devices that allow the user to input information to indicate whether the user is in the walking state or in the running state. However, there is a problem in view of the user's convenience as the input is needed when the user changes the state of movement. Accordingly, in recent years, automatic judgment systems are used to automatically judge the state of movement.
For example, according to JP-A-2011-221798 (Patent Document 1), the walking state or the running state is judged by measuring the time interval of pulse signals that correspond to steps in walking or in running. Also, according to JP-A-2008-077368 (Patent Document 2), when processing pulses corresponding to steps, a filter that can pass different frequency bands is used, thereby discriminating walking that is to be detected with a lower frequency from running that is to be detected with a higher frequency.
The methods described in Patent Document 1 and Patent Document 2 are both based on the idea that the time interval of the steps in the running state is longer than that in the walking state. However, the pitch in walking and running greatly differs from one person to another. There could be cases where the time interval between the steps is very short even in the walking state (race-walk, as an extreme example), or where the time interval between the steps is relatively long even in the running state (for example, the stride-running technique). Therefore, there is a danger of misjudgment in the techniques that are based on the time interval in the steps.